Measles: What you need to know about the virus

It's widespread -- from Northland to Nelson, with Waikato thrown in between -- and it's serious. Three schools have closed and a quarter of the Waikato cases have required hospitalisation.

Measles has never been eradicated in New Zealand, unlike in other Western countries.

Herd immunity -- the ability of a population to protect itself -- requires 95 percent of the population to be vaccinated.

While New Zealand's overall rate is getting close to that figure, there remain large pockets that fall well below that -- and those pockets include teenagers and young adults.

Measles is also dangerous because it's highly contagious.

While someone carrying the Ebola virus will infect another two people and a person with a common cold will infect approximately six, someone with measles -- in an unvaccinated population -- can infect up to 18 people.

Story myth-busts the measles and explains why you should get clued up on the virus.